In recent years, hybrid electric vehicles (HEVs) and electric vehicles (EVs) have been generalized to some degree, and charging facilities for charging storage batteries installed in such vehicles are widely used along with the generalization of such vehicles. In this regard, as a related art, there has been disclosed a technique which turns On/Off a main relay of a charging cable (power line) using a control pilot line (CPLT line; communication control line) in order to control charging a storage battery installed in a vehicle (for example, see Patent Literature (hereinafter, abbreviated as PTL) 1). According to this technique, turning on the main relay of the charging cable in a time slot for which electric power charge is low, based on power information acquired from an external power supply of a vehicle through the CPLT line allows a storage battery of the vehicle to be appropriately charged while keeping the cost required for charging low. Note that, although a charging process flow using the CPLT line is defined in ISO/IEC 61851 standard and SAE J1772 standard, which are joint connect standards of EVs and HEVs, a description thereof will be omitted herein.
In addition, as another related art, a technique that monitors the state of charge of a storage battery installed in a vehicle using power line communication (PLC) which uses a power line as a communication line has been disclosed (for example, see PTL 2). According to this technique, before the storage battery installed in the vehicle is charged, a communication connection using a power line with a vehicle ID, i.e., PLC is established. Then, disconnection of a charging cable (power line) or the like occurs during a charging process, a cable disconnection detection signal indicating disconnection of a changing cable during the charging process, monitoring information indicating the state of the vehicle, and the vehicle ID are transmitted from a charging control apparatus of the vehicle to an external charging station through communication (PLC) using the charging cable. Accordingly, when disconnection of a charging cable (power line) occurs during a charging process in an environment in which a plurality of vehicles are charged at a single charging station, a vehicle and a state in which the disconnection of the charging cable occurs can be instantly monitored and determined on the charging station side. As described above, the establishment of communication connections using PLC which transmits information signals while superimposing one on top of another in an overlapping manner between the vehicle and subscriber equipment (charging station) through an infrastructure facility (in other words, the power line) enables charging control while the storage battery installed in the vehicle is appropriately monitored.